What effect does Parkinson's disease have on the eyes or vision?

Parkinson’s disease can affect vision in many ways. A slower blink can cause symptoms of a dry eye and loss of vision due to a poor quality tear film. Initial treatment is usually lubricating drops. However, there are many other causes of visual loss, visual fatigue and reading difficulty in Parkinson’s disease. Parkinson’s disease can affect the extraocular motility making eye tracking, required for reading, much more difficult.  Optic neuropathy or a deterioration of the optic nerve has also been seen in Parkinson’s disease.